‘He might,’ Albert admitted.  ’But don’t forget this is all theory.  I suppose you’ve been making your own inquiries in the Medical Department?’

‘Yes,’ said Simon rather apologetically.  ’But I couldn’t find anyone among the staff who remembers serving such a man, or even seeing him.  He may have had an accomplice, you know, on the staff.  What makes it more awkward is that there were two photographs taken, one about eleven, and another about half-past, and the photographer got the plates mixed up, and doesn’t know whether this one is the first or the second.  You see, the clock doesn’t show in the picture; otherwise, we might have pieced things together.’

‘Pity!’ Albert murmured.

‘However,’ said Simon, with an obvious intention to be dramatic, ’I thought of Lecoq, and I hit on something.  You see the lady just leaving the cash-desk with her receipt?  Can you read the number of her receipt?’

Albert peered.

‘No, I can’t,’ he said.

‘Neither could I,’ Simon agreed.  ’But I’ve had that part of the photograph enlarged to-night.’

‘The deuce you have!’ Albert opened his eyes.

‘Yes, the deuce I have!  And here it is.’

Simon took a photographic print from his pocket, showing the lady’s hand and part of the receipt, very blurred and faint, with some hieroglyphic figures mistily appearing.

‘Looks like 6,706,’ said Albert.

‘It’s either 6,706 or 6,766,’ Simon concurred.  ’Now, Ravengar’s receipt must be numbered next to hers.  Consequently, if we go and look at the counterfoils and duplicates—­’

‘Yes,’ said Albert, thoughtfully sliding down from the piano.

‘We may be able to find out something very interesting,’ Simon finished, descending also.

‘Now?’

’Now.  That’s what I wanted you for.  You’ve got your pass-keys and everything, haven’t you?’

‘Yes.’

‘Then run down and search.’

‘Aren’t you coming too?’

‘I was only thinking, suppose the governor came back and wanted me?’

Albert gazed contemptuously at this exhibition of timidity—­the cowardice of a born valet, he deemed it.

‘Oh, of course,’ he exclaimed, ‘if you—­’

‘I’ll come,’ said Simon boldly.  ’If he wants me he must wait, that’s all.’

They descended together in Hugo’s private lift, direct from the dome; the Medical and Pharmaceutical Department was on the ground-floor.  Simon acted as lift-man, and slammed the grill when they emerged.

‘Just open that again, Si,’ Albert requested him.

‘Why?  What’s up?’

‘Just open it.’

Albert was sniffing about like a dog that is trying to decide whether there is not something extremely attractive in the immediate neighbourhood.  He re-entered the lift, and nosed it curiously.

Suddenly he bent down and peered under the cushioned seat of the lift, and drew forth an object that resembled in shape a canister of disinfectant powder.